Complexity speed run to stagnation isn’t suspect at all, thats exactly what you’d expect when there is suddenly a new environment to exploit for life. Mutations

Complexity speed run to stagnation isn’t suspect at all, thats exactly what you’d expect when there is suddenly a new environment to exploit for life. Mutations are always happening. At some point a subpopulation will emerge that has a lucky few mutations that grant it an edge relative to others in fitness, then it will dominate the environment until the factors that confer success either change, or these mutants fall short of a more fit upstart mutant population. Its something you see play out even today, when an invasive species is introduced to a new environment where its traits serve it well, and quickly outcompetes native species. Its also why we better be damn sure the mars sample return is absolutely sterile lest we contaminate our planet with extraterrestrial microbes.